Varicella-zoster virus, also sometimes referred to as herpes zoster, produces infection in a manner similar to that of HSV. After a primary infection, VZV remains latent in dorsal root ganglia; host cellular immune interaction inhibits reactivation. Primary infection usually occurs in childhood in the form of chickenpox (varicella), a generalized vesicular rash accompanied by mild constitutional symptoms. Reactivation may be heralded by pain in a sensory nerve distribution, followed by a unilateral vesicular eruption occurring over 1 to 3 dermatomic areas. New crops of lesions appear in the same area within 7 days. Resolution of the lesions may be followed by postherpetic neuralgia. Other neurologic sequelae following VZV reactivation include segmental myelitis, Guillain-Barré syndrome, and Ramsay Hunt syndrome. The incidence of VZV is 2 or 3 times higher in patients older than 60 years. Postherpetic neuralgia occurs after VZV infection in approximately 50% of patients older than 50 years. The pain of postherpetic neuralgia can be severe and debilitating and may persist for months or even years. Immunosuppressed persons experience recurrent lesions and an increased incidence of disseminated disease.
For immunocompetent adults with cutaneous VZV infection, recommended 7-day treatment regimens include famciclovir (500 mg twice a day), valacyclovir (1000 mg 3 times a day), and acyclovir (800 mg 5 times a day). Treatment of acute infection in immunocompromised patients or those with visceral involvement may include acyclovir, famciclovir, or valacyclovir. Newer drugs being evaluated for resistant VZV strains or concomitant HIV infection include sorivudine, brivudine, fialuridine, fiacitabine, netivudine, lobucavir, foscarnet, and cidofovir.
Varivax, a live attenuated varicella-zoster vaccine, is available for use in children for prevention of primary disease. The CDC recommends Shingrix, a recombinant zoster vaccine given in 2 doses separated by 2 to 6 months, for the prevention of shingles in immunocompetent adults aged 50 years and older. Please see Chapter 12 in this volume for further discussion of varicella zoster vaccines.
In some patients, tricyclic antidepressants, pregabalin, gabapentin, and topical capsaicin cream reduce the pain of postherpetic neuralgia. For refractory cases, transcutaneous electronic nerve stimulation, nerve blocks, or intrathecal glucocorticoid injections may be helpful.
Finnerup NB, Attal N, Haroutounian S, et al. Pharmacotherapy for neuropathic pain in adults: a systematic review and meta-analysis. Lancet Neurol. 2015;14(2):162–173.
Excerpted from BCSC 2020-2021 series: Section 1 - Update on General Medicine. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.